I really like the contrast with the red as well, but I feel that the composition of this one is a little too balanced, too centered with the stem coming out of the middle of the frame. There is so much detail to the left of the stem, in the petals and the greenery, but on the right the DOF fades quickly, making it feel a little less powerful than it could be.
Even a slight crop of the right side, to take away some of the red would add strength to the comp.
Thanks so much for this awesome display of Gerbera's though... they are tied with sunflowers as my most fave flower, and this series you've done really lets them shine!